In recent years, an operating voltage of a semiconductor circuit has been reduced along with miniaturization, and a digital circuit can be operated at 1.0 V or lower. Moreover, in the digital circuit, power consumption in the operation of the circuit can be reduced by reducing a power supply voltage or an operating speed. Because of such a background, utilization of the circuit for an energy harvesting system such as a solar cell has been paid attention. As a power supply adjusted to such an energy harvesting system, a digitally-controlled power supply has been paid attention.
As a conventional technique, for example, the power supply circuit illustrated in FIG. 1 of Japanese Patent Application Laid-Open Publication No. 2012-63810 (Patent Document 1) which has been previously applied by the present inventor is known.